title: Kinetic modelling of the Zymomonas mobilis Entner-Doudoroff pathway: insights into control and functionality.
abstract: Zymomonas mobilis, an ethanol-producing bacterium, possesses the Entner-Doudoroff (E-D) pathway, pyruvate decarboxylase and two alcohol dehydrogenase isoenzymes for the fermentative production of ethanol and carbon dioxide from glucose. Using available kinetic parameters, we have developed a kinetic model that incorporates the enzymic reactions of the E-D pathway, both alcohol dehydrogenases, transport reactions and reactions related to ATP metabolism. After optimizing the reaction parameters within likely physiological limits, the resulting kinetic model was capable of simulating glycolysis in vivo and in cell-free extracts with good agreement with the fluxes and steady-state intermediate concentrations reported in previous experimental studies. In addition, the model is shown to be consistent with experimental results for the coupled response of ATP concentration and glycolytic flux to ATPase inhibition. Metabolic control analysis of the model revealed that the majority of flux control resides not inside, but outside the E-D pathway itself, predominantly in ATP consumption, demonstrating why past attempts to increase the glycolytic flux through overexpression of glycolytic enzymes have been unsuccessful. Co-response analysis indicates how homeostasis of ATP concentrations starts to deteriorate markedly at the highest glycolytic rates. This kinetic model has potential for application in Z. mobilis metabolic engineering and, since there are currently no E-D pathway models available in public databases, it can serve as a basis for the development of models for other micro-organisms possessing this type of glycolytic pathway.
authors.affiliation: Institute of Microbiology and Biotechnology, University of Latvia, Kronvalda Boulv. 4, Riga LV-1586, Latvia.
authors.forename: Reinis
authors.initials: R
authors.lastname: Rutkis
authors.affiliation: Institute of Microbiology and Biotechnology, University of Latvia, Kronvalda Boulv. 4, Riga LV-1586, Latvia.
authors.forename: Uldis
authors.initials: U
authors.lastname: Kalnenieks
authors.affiliation: Biosystems Group, Department of Computer Systems, Latvia University of Agriculture, Liela Iela 2, Jelgava LV-3001, Latvia.
authors.forename: Egils
authors.initials: E
authors.lastname: Stalidzans
authors.affiliation: Department of Biological and Medical Sciences, Oxford Brookes University, Headington, Oxford OX3 0BP, UK.
authors.forename: David A
authors.initials: DA
authors.lastname: Fell
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D000426:Alcohol Dehydrogenase / Q000235:genetics / Q000378:metabolism; D002245:Carbon Dioxide / Q000378:metabolism; D003198:Computer Simulation; D000431:Ethanol / Q000378:metabolism; D015964:Gene Expression Regulation, Bacterial; D005947:Glucose / Q000378:metabolism; D053858:Metabolic Networks and Pathways / Q000235:genetics*; D008954:Models, Biological; D011767:Pyruvate Decarboxylase / Q000235:genetics / Q000378:metabolism; D017355:Zymomonas / Q000201:enzymology / Q000235:genetics* / Q000378:metabolism*
chemical_list: D002245:Carbon Dioxide; D000431:Ethanol; D000255:Adenosine Triphosphate; D000426:Alcohol Dehydrogenase; D011767:Pyruvate Decarboxylase; D005947:Glucose